The present invention relates to a circuit board enhanced in heat dissipation characteristics, its manufacturing method, and an electronic apparatus using the same.
Recently, in the trend of electronic apparatus becoming higher in performance and smaller in size, electronic components such as semiconductors and the like are required to be high density and to have multiple functions. The circuit board on which they are mounted is also desired to be smaller in size and high density. As a result, it is an important problem how to dissipate the heat generated in power semiconductors and the like mounted at high density.
To improve the heat dissipation characteristic, for example, the prior arts shown in FIG. 8 and FIG. 9 are known. In FIG. 8 and FIG. 9, the conventional circuit board improved in heat dissipation characteristic is composed of a metal plate 11, an insulation layer 12, a conductor foil 13, electronic components 14 including a power semiconductor, and external connection terminals 15.
The conductor foil 13 is adhered to the metal plate 11 by way of the insulation layer 12. This conductor foil 13 is etched and formed into a circuit pattern. Heat generated from electronic components 14 is transferred to the metal plate 11 through the insulation layer 12. A radiator 16 is used to assist the heat dissipation if it is insufficient with the metal plate 11 alone.
In the conventional configuration, the heat dissipation characteristic of the circuit board is determined by a thickness of the conductor foil 13 and the insulation layer 12 formed between the metal plate 11 and the conductor foil 13, and therefore the heat dissipation characteristic could not be enhanced sufficiently.
The present invention is intended to address the above problem, and it is hence an object of the present invention to provide a circuit board enhanced in the heat dissipation characteristic and an electronic apparatus using the same.
The circuit board of the present invention comprises a sheet made of composite resin (hereinafter called sheet), and a metal plate overlaid on this sheet, wherein the metal plate forms circuit patterns. As the metal plate, copper or copper alloy of excellent heat conductivity is preferably used. The sheet is composed of 70-95 parts by weight of inorganic filler, and 5-30 parts by weight of resin composition containing thermosetting resin and a hardener. The sheet may contain, if necessary, a hardening accelerator. The metal plate is roughened and reinforced for adhesion at least on one surface adhering to the sheet.
In the circuit board of the present invention, the composite resin fills the spaces between the circuit patterns, and a plane is formed by the composite resin and the metal plate at a surface of the metal plate for mounting components. Also in the circuit board of the present invention, since the composite resin containing the inorganic filler is also present between the circuit patterns composed of the metal plate, its heat dissipation characteristic is very high, and it is suited as a circuit board for electronic apparatus such as power circuits which contain heat generating components.